The present invention relates to a pump for exerting pressure on fluid and particularly relates to a circulation of the fluid through the pump.
Unexamined Japanese Patent Publication No. 9-88807 discloses a pump for exerting pressure on fluid. The pump has an integral structure that includes a hydraulic pump (a pump mechanism) and an electric motor (a motor mechanism) in the same unit housing. The pump also includes an oil passage for draining oil from the hydraulic pump into the electric motor side and then to the outside of the housing. Thus, the drain oil cools the electric motor. However, an introducing port for introducing oil from the outside of the housing into the inside is not provided, and only the drain oil drained from the pump cools the motor. Since cooling is performed only by the drain oil, cooling efficiency is relatively low.
Unexamined Japanese Utility Model Publication No. 4-57693 also discloses a fluid pump. The fluid pump includes a pump mechanism and a motor mechanism. The fluid pump also includes two communication passages bored through a casing of the fluid pump, and the communication passages are located adjacent to the motor mechanism. The fluid enters into the casing through one passage and exits through the other to cool the motor mechanism.
It is desired to obtain a pump for exerting pressure on fluid that efficiently cools a pump mechanism and a motor mechanism and to obtain a fluid tank unit with the above pump.